Process for the extraction of gallium

ABSTRACT

Gallium is efficiently extracted from strongly basic solutions containing aluminates by extractants having the tris- and/or tetrakis(2-hydroxybenzyl)-1,2-diaminoethane chemical moiety. The diaminoethane derivative may be used together with a hydrocarbyl 8-hydroxyquinoline and/or with a tertiary carboxylic acid.

This is a division of application Ser. No. 07/884,230, filed May 11,1992 now U.S. Pat. No. 5,183,940 which in turn is a continuationapplication of application Ser. No. 07/068,136, filed Jun. 29, 1992, nowabandoned.

This invention is concerned with new compounds which are suitable foruse in metal extraction processes, a metal extraction process using suchcompounds, and particularly a process to extract gallium contained instrongly basic aqueous feed solutions, for example solutions of sodiumaluminate more particularly such solutions obtained from the Bayerprocess for production of alumina.

It is known to extract metals, for example copper or gallium, fromaqueous solutions containing the metal by contacting the aqueoussolution with a solution of an extractant in a water immiscible solventand then separating the solvent phase loaded with metal, i.e. containinga part of the metal in the form of a chelate compound with theextractant. The extracted metal can then be recovered from the metalloaded solvent phase by stripping with acid solutions followed, forexample, by electrowinning.

The prior art preferred extractant for gallium is a compound availableas KELEX 100 which is a 7-hydrocarbyl-8-hydroxyquinoline as disclosed inBritish Patent 1513398. A similar extractant is available as LIX-26.More particularly, compounds of this type are used for the extraction ofgallium from Bayer process aluminate solutions which are strongly basicsolutions containing aluminium and gallium in a weight ratio whichtypically varies from 150 to 1 to 400 to 1. Due to the selectivity ofthe extractant for gallium, a substantially smaller ratio is obtained inthe organic solution after the extraction step. The use of7-hydrocarbyl-8-hydroxyquinoline provides a very slow rate of extractionand a number of additives have been proposed in order to increase thekinetic rate of extraction. Such additives comprise organs-phosphorus,sulphate or sulphonate compounds and are described in European PatentApplications 0102882 and 0102880. Tertiary carboxylic acids are alsodisclosed as increasing the rate of extraction, as described in moredetail in United States Patent No.4241029. The use of 7-hydrocarbyl-8-hydroxyquinoline has also been found to require the use of a stripsolution containing a large excess of acid in order to effect transferof the gallium from the organic extractant solution into the aqueousstrip solution.

We have now found organic compounds of entirely different chemicalstructure from 7-hydrocarbyl-8-hydroxyquinoline which are goodextractants for gallium and some of which give a higher rate ofextraction than is achieved with the quinoline derivative. Furthermore,using the new extractants, only a slight excess of acid is required torecover the gallium from the organic extractant phase into the aqueousstrip solution.

According to the present invention there is provided a compound of thegeneral formula (A): ##STR1## wherein: Q is a hydrogen atom, ahydrocarbyl group, a substituted hydrocarbyl group or a group --CH₂ Z;

Z is a --COOH group or a 2-hydroxyphenyl group which may optionally besubstituted by the groups R₁₂, R₁₃ and R₁₄ ;

R₁ to R₉, and R₁₂ to R₁₄, which may be the same or different aresubstituent groups;

R₁₀ and R₁₁ are each, independently, a hydrogen atom or an alkyl groupcontaining up to 20 carbon atoms;

Y₁ is a hydrogen atom, or an alkyl group containing up to 20 carbonatoms, or a phenyl group;

Y₂ is a hydrogen atom or an alkyl group containing up, to 20 carbonatoms, or Y₁ and Y₂, together with the group ##STR2## form a saturatedor unsaturated ring system; and R₁ to R₁₄, Y₁ and Y₂ are the same ordifferent and together contain in total from 10 to 60 saturated carbonatoms.

The substituents R₁ to R₉ and R₁₂ to R₁₄ are independently hydrogen;hydrocarbyl; alkoxy such as methoxy or 2-hexyldecyloxy; halogen such aschloro or bromo; hydrocarbyl sulphonyl such as methyl sulphonyl ordodecylbenzenesulphonyl; acyl such as acetyl or octanoyl; amino;alkylamino; di-alkylamino such as di-octylamino; alkylacylamino;acylamino such as acetylamino; nitro and cyano, particularly thosecontaining 1 to 20 carbon atoms and especially those containing 6 to 20carbon atoms. R₁ and R₂ and/or R₄ and R₅, if adjacent substituents, maycomplete a benzo ring so that the corresponding phenyl ring depictedbecomes a part of a naphthyl ring.

Without disadvantage in the practice of the invention, the substituentsR₁ to R₉ and R₁₂ to R₁₄ may be hydrocarbyl groups which are furthersubstituted by groups which are sufficiently inert in the presence ofaqueous alkali, for example alkoxy groups. It is preferred however thatthe substituents R₁ to R₉ and R₁₂ to R₁₄ are hydrogen atoms orunsubstituted hydrocarbyl groups, particularly alkyl groups such asethyl, propyl, isopropyl, n-butyl, tertiary butyl, isopentyl, hexyl,heptyl, octyl, 2-hexyldecyl, isooctadecyl and 2-octyldodecyl. It isespecially preferred that the alkyl groups should be methyl or the mixedand highly branched higher tertiary alkyl groups such as tertiary octyl,tertiary nonyl and tertiary dodecyl which are obtained by alkylation ofphenols with the mixed olefins which are commercially available.

The group Q may be a hydrogen atom or a hydrocarbyl, particularly amethyl, group. However, it is generally preferred that Q is a group--CH₂ Z and, in particular, one in which Z is an optionally substituted2-hydroxyphenyl group.

The groups Y₁ and Y₂ may, together with the group ##STR3## form a ringsystem, particularly a six membered saturated ring system with thesubstituted nitrogen atoms being linked to the ring in the 1,2 position.However, it is preferred that the groups Y₁ and Y₂ do not form a linkinggroup connecting the substituted nitrogen atoms. It is preferred that atleast one of Y₁ and Y₂ is a hydrogen atom. Thus, particularly preferredcompounds are those in which Y₁ is hydrogen, a methyl group or a phenylgroup and Y₂ is hydrogen.

The groups R₁₀ and R₁₁ are preferably the same to facilitate productionof the compound and it is particularly preferred that both R₁₀ and R₁₁are hydrogen.

To facilitate manufacture of the diamino compound of the presentinvention it is preferred that R₃, R₆, R₉ and R₁₄ are hydrogen and thatR₁ and R₄ are the same, R₂ and R₅ are the same, R₇ and R₁₂ are the sameand R₈ and R₁₃ are the same. The substituents which are not hydrogen oralkyl groups are preferably methoxy or nitro groups or especially chloroor bromo groups. The substituents should be predominantly located inpositions ortho or para to the phenolic OH groups.

N,N,N',N'-tetrakis-(2-hydroxybenzyl)-1,2-diaminoethane, which is theparent compound of certain of the diamino compounds of the presentinvention, has been reported by C. G. Pitt and G. Gupta inJ.Pharmacol.Exp.Theory 208(1) 12-18 1979, but no reports of its metalcomplexing properties have appeared.

As is discussed in more detail hereafter, the diamino compounds of thepresent invention are extractants for gallium. However, the diaminocompounds can be used with other compounds to give an increased rate ofextraction. More specifically, certain diamino compounds in accordancewith the present invention, for exampleN,N'-bis-(2-hydroxybenzyl)-N,N'-bis(2-hydroxy-5-tertiarynonylbenzyl)-1,2-diaminoethane, may be used as catalysts to increase therate of extraction of gallium by other extractants which are themselvesslower to extract gallium. The primary extractant, whose rate ofextraction is to be increased, may itself be a diamino compound inaccordance with the invention, or may be a quite different compound suchas an 8-hydroxyquinoline derivative, for example a7-hydrocarbyl-8-hydroxyquinoline material available either under thetrade name Kelex 100 or under the trade name LIX-26. The hydrocarbylgroup is typically an alkyl or alkenyl group or a mixture thereof. Ingeneral the hydrocarbyl group contains at least 6 carbon atoms and notmore than 36 carbon atoms, especially from 9 to 24 carbon atoms, forexample nonyl, decyl, undecyl, dodecyl, dodecenyl, tridecyl, tetradecyl,octadecyl and the like. If it is being used as a catalyst, it isconvenient to add the diamino compound in an amount from 1 to 30% byweight of the weight of primary extractant which is used.

The rate of extraction of gallium using the diamino compounds may beincreased by adding an additive to the diamino compound, such additivebeing, in particular, a carboxylic acid, a sulphur-containing acid or aphosphorus-containing acid. Particularly useful increases in theextraction rate have been attained using a tertiary carboxylic acid,that is a compound having a tertiary group attached directly to thecarboxylic acid group. Compounds of this type are of the generalformula: ##STR4## wherein R₁₅, R₁₆ and R₁₇ may be the same or differentand are hydrocarbyl or substituted hydrocarbyl groups.

The groups R₁₅, R₁₆ and R₁₇ are preferably alkyl or substituted alkylgroups. The substituents, if present, are hydrocarbonoxy or nitro groupsor halo groups such as chloro or bromo. It is preferred that the groupsR₁₅, R₁₆ and R₁₇ together contain at least 5 carbon atoms, for exampleat least 8 carbon atoms. No particular advantage is gained if the groupsR₁₅, R₁₆ and R₁₇ together contain more than 45 carbon atoms. We haveobtained a useful increase in the rate of extraction of gallium when thediamino compound is used together with a mixture of tertiary carboxylicacids having an average composition of C₉ H₁₉ COOH.

The tertiary carboxylic acid is used as a catalyst to increase the rateof extraction of the diamino compound and is conveniently used in anamount of from I to 30% by weight relative to the weight of the diaminocompound.

A mixture of the diamino compound with a compound effective to increasethe extraction rate of gallium may be used as a catalyst for anextractant having a lower rate of extraction, for example a mixture ofthe diamino compound with a catalytic amount of a tertiary carboxylicacid may itself be added in a catalytic amount to an 8-hydroxyquinolinederivative.

Thus, as a further embodiment of the present invention there is provideda composition which comprises a diamino compound as hereinbeforedescribed, and at least one of an 8-hydroxyquinoline derivative, acarboxylic acid, a sulphur-containing acid and a phosphorus-containingacid.

Sulphur-containing acids which may be used include aryl sulphonic acidssuch as naphthalene sulphonic acid, for example bis(dodecyl)naphthalenesulphonic acid. Phosphorus-containing acids which may be used includephosphoric acid and the partial esters thereof such as thebis(2-ethylhexyl) ester of phosphoric acid.

A preferred composition comprises a diamino compound, a 7-alkyl and/or7-alkenyl-8-hydroxyquinoline derivative and a tertiary carboxylic acid.The components of the composition are conveniently present in theproportions of from 1 to 50% by weight of the tertiary carboxylic acidrelative to the weight of the quinoline compound and from 1 to 30% byweight of the diamino compound relative to the weight of the quinolinederivative. Preferably the tertiary carboxylic acid is used in theproportion of 10 to 40% by weight relative to the quinoline compound.Preferably, the diamino compound is used in the proportion of 5 to 20%by weight of the quinoline derivative.

The diamino compounds of the invention may be prepared for example byreacting a substituted salicylaldehyde of the general formula I with adiamine of formula II to form a double Schiff's base of formula IIIwhich may be reduced by sodium borohydride or, in suitable cases byhydrogenation to the compound of formula IV, following the generalprocedures described in U.S. Pat. No. 4,338,460. Compound IV may then bereacted either with a suitably substituted acetoxybenzyl bromide V andthe product hydrolysed with sodium hydroxide to give the requiredcompound VI following procedures parallel to those described in U.S.Pat. No. 3,632,637. Alternatively compound IV may be reacted withformaldehyde and a suitably substituted phenol VII in a fashion similarto that described in U.S. Pat. Nos. 3,038,793 and 4,338,460 in order togive compound VI; this alternative works best if the phenol VII hassubstituents in at least the para position. ##STR5##

In those cases where R₁, R₂, R₃, R₇, R₈ and R₈ are not identical withR₄, R₅, R₆, R₁₂, R₁₃ and R₁₄ respectively or where the group Q is --CH₂Z where Z is --COOH, a more complicated procedure is required. Thesecompounds may be prepared for example by subjecting a monoamide VIII tothe procedures outlined above, but using only one equivalent of theother reactants, in order to prepare a substituted amide IX. Thepropionyl protecting group may then be removed by hydrolysis to form thecorresponding amine X which is reacted with a substitutedsalicylaldehyde XI and then reduced as described previously to give theextractant XII. Compound XII may be reacted with an o-acetoxybenzylbromide XIII and then hydrolysed as previously described to give analkane diamine derivative where Q is --CH₂ Z and Z is a group ##STR6##

Alternatively, compound XII may be reacted with formaldehyde and asubstituted phenol XIV to give the same, or an analogous, alkane diaminoderivative.

As a further alternative, the compound XII may be reacted with ethylmonochloroacetate or glycollonitrile and then hydrolysed to give anethane diamino derivative where Q is --CH₂ Z and in which Z is --COOH. Asimilar procedure using glycollonitrile (HOCH₂ CN) is described in U.S.Pat. No. 4338460. ##STR7##

Several modifications or alternatives to these procedures will beobvious to those skilled in the art, thus chloro, bromo and nitrosubstituents if required may be introduced by reaction of chlorine,bromine and nitric acid respectively with intermediates such as IV, X,XII or with VI or with a compound of the general formula A as the finalreaction step. As a further modification, the compound of formula IV maybe reacted with 2-hydroxybenzylalcohol to give a produce which ispredominantly the tetraphenol of formula VI. However, using thisprocedure the purity of the tetraphenol VI is generally lower than isobtained when an optionally substituted acetoxybenzyl bromide is usedand subsequently hydrolysed. We have found that the less pure producthas a lower capacity for the extraction of gallium than the purerproduct obtained using acetoxybenzyl bromide but gives essentially thesame effect if used as a rate-increasing catalyst for a primaryextractant such as an 8-hydroxyquinoline derivative.

The preferred compounds of the present invention are the tetraphenolssuch as the tetraphenol of formula VI. Bis phenols, such as the compoundof formula IV, have been found to possess little or no activity whenused for the extraction of gallium.

The reaction procedures used to synthesize the products of the inventiongive rise to by-products. When synthesising tetraphenols, theby-products include triphenols, that is compounds of the general formula(A) in which the group Q is a hydrogen atom. Other by-products includelow polymers in which compounds of the general formula (A) are linked tothemselves, or to other phenolic moieties derived from the startingmaterials by, for example, methylene groups or substituted methylenegroups. Thus, many of the by-products are, essentially, compounds of thegeneral formula (A) which are further substituted. Compounds of thistype are believed to contribute to the uptake of gallium by the productmixture and also to effect the rate at which gallium is extracted.Removal of the by-products from the desired material is difficult anduneconomic. However, since the presence of the by-products does notappear to have a significant deleterious effect on the extraction ofgallium, removal of the by-products is generally unnecessary.

According to a further aspect, the invention is also concerned with aprocess of extracting gallium from basic aqueous solutions.

According to this further aspect there is provided a process forextracting gallium from a basic aqueous solution containing gallium,such process comprising the steps of

(a) contacting an aqueous solution containing gallium with a solution ina water immiscible solvent of at least one diamino compound of thegeneral formula A, as hereinbefore defined;

(b) separating the aqueous phase from the solvent phase which contains agallium complex compound;

(c) contacting the solvent phase with an aqueous mineral acid (strippingstage) or with an alkaline aqueous solution which is more stronglyalkaline than the aqueous solution of steps (a) and (b); and

(d) separating the solvent phase from the aqueous phase containing metalin the form of a salt of the mineral acid or of an oxyanion.

The first step of the process may conveniently be carried out bybringing together the aqueous solution and a solution containing atleast one diamino compound of the general formula A, which may be a tri-or tetraphenol or a mixture thereof in the organic solvent. Thecontacting may be effected at any suitable temperature, for example fromambient temperature up to 100° C., and preferably in the range from 40°C. up to 70° C. The contacting is preferably effected by agitating orotherwise disturbing the mixture of liquids so that the area of thewater-solvent interfacial layer is increased in order to promote complexformation and extraction, and then decreasing the agitation ordisturbance so that the aqueous and solvent layers settle and can beconveniently separated. The process may be carried out in a batchwisemanner or continuously.

The amount of organic solvent to be used may be chosen to suit thevolume of aqueous solution to be extracted, the concentration of metals,and the plant available to carry out the process. It is preferred,especially when operating the process continuously, to bring togetherapproximately equal volumes of the organic solution and the aqueoussolution.

Examples of suitable water-immiscible organic solvents are aliphatic,aromatic and alicyclic hydrocarbons, chlorinated hydrocarbons such asperchloroethylene, trichloroethane and trichloroethylene. Mixtures ofsolvents may be used. Especially preferred in conventionalhydrometallurgical practice are mixed hydrocarbon solvents such as highboiling, high flash point petroleum fractions (for example kerosene)with varying aromatic content. In general, hydrocarbons having a higharomatic content, for example AROMASOL H which consists essentially of amixture of trimethylbenzenes and is commercially available from ImperialChemical Industries PLC (AROMASOL is a trade mark) or SOLVESSO 150 whichis 98% by volume an aromatic fraction, has a boiling point range of 190°C. to 210° C. and is commercially available from Esso (SOLVESSO is atrade mark), provide a higher solubility than kerosene for theextractant and its metal complex, whilst a kerosene having a relativelylow aromatic content, for example ESCAID 100 which is petroleumdistillate comprising 20% aromatics, 56.6% paraffins and 23.4%naphthenes commercially available from Esso (ESCAID is a trade mark) mayin certain cases improve the hydrometallurgical performance of theextractant. Factors influencing the solubility of the extractant and itsmetal complex are complicated, but in general extractants having highlybranched substituents and/or an isomeric mixture of substituents havecomparatively high solubility. The concentration of the extractant inthe water immiscible organic solvent may be chosen to suit theparticular aluminate solution to be treated. Typical values ofextractant concentration in the organic phase are between 5 and 300g/liter and an especially convenient range is from 20 to 200 g/liter.

The solvent is preferably a hydrocarbon having a high aromatic contentbut we particularly prefer to use a solvent which contains an alkanol,especially a higher alkanol which is soluble in the hydrocarbon solventand of low solubility, or insoluble, in water. Preferred alkanols arethose in which the alkyl group contains at least 6 carbon atoms andespecially which contains at least 8 carbon atoms. The alkyl group ofthe alkanol typically does not contain more than 36 carbon atoms andespecially contains not more than 24 carbon atoms. Alkanols which may beused as part of the solvent include octanol, nonanol, n-decanol,iso-decanol, dodecanol, tridecanol, hexadecanol and octadecanol.Particularly useful results have been obtained when the alkanol isn-decanol. The alkanol, if present in the solvent is preferably presentin an amount of at least 5% by volume of the solvent mixture. Typically,the alkanol is not present in an amount of more than 50% by volume ofthe solvent mixture and especially does not exceed 30% by volume of thesolvent mixture. The presence of an alkanol in the solvent mixturegenerally results in an improvement in the solubility of the complex ofthe metal with the extractant and can also result in improveddisengagement of the organic and aqueous phases. We have also foundthat, during stripping of the organic phase with an aqueous acid, saltseparation may occur, particularly with a strip solution containingsulphuric acid. The presence of an alkanol in the organic phase reduces,or even prevents, salt separation during the stripping with the aqueousacid.

We have also found that if the organic phase includes a sulphur- orphosphorus-containing acid, the presence of such compounds also reducessalt separation during stripping with an aqueous acid such as sulphuricacid.

As previously noted herein, the diamino compound of the general formulaA may be used in conjunction with other materials which are eitherextractants themselves and/or which catalyse the rate of extraction ofgallium from the aqueous solution. Hence, in step (a) of the process,the solution in the water immiscible solvent may contain, in addition toat least one diamino compound of the general formula A, at least oneother material which is itself an extractant and/or is effective toincrease the rate of extraction of gallium from the aqueous solution.

In particular, in step (a) of the process, the solution in the waterimmiscible solvent contains, in addition to at least one diaminocompound of the general formula A, at least one further compound whichis selected from an 8-hydroxyquinoline derivative, a carboxylic acid, asulphur-containing acid and a phosphorus-containing acid. Moreparticularly, at least one further compound is a 7-alkyl and/or7-alkenyl-8-hydroxyquinoline and/or a tertiary carboxylic acid.

The diamino compound used in the process of the present invention ispreferably a tetraphenol particularlyN,N'-bis(2-hydroxybenzyl)-N,N'-bis(2-hydroxy-5-tertiarynonylbenzyl)-1,2-diaminoethaneand especiallyN,N'-bis(2-hydroxybenzyl)-N,N'-bis(2-hydroxy-5-tertiary-nonylbenzyl)-1,2-diaminopropane.

The stripping step may be performed with a mineral acid in water and, inthe case of the presence of aluminium, both metals will be recovered.The alternative possibility of stripping with a concentrated aqueousalkaline solution (for example 10 molar NAOH) may also be envisaged inorder to obtain differential stripping.

Concentrated hydrochloric acid may also be used in some cases, thegallium then being retained as anion Ga(Cl₄)⁻ associated with theprotonated extractant of the invention.

We have found that, if the stripping step is effected using a mineralacid in water, only a slight excess of acid is necessary in order torecover most of the gallium, typically an excess aqueous concentrationof 0.1 to 0.2N over that stoichiometrically required to react with themetal complexes in the organic solution. In contrast to this, using an8-hydroxyquinoline derivative requires a substantial excess of acid torecover most of the gallium, typically an excess aqueous concentrationof 2N to 3N of the acid.

We have also found that the nature of the metal stripped from theorganic phase is dependent on the amount of acid added. Thus, as theamount of acid added to the stripping stage is increased, the metalspresent in the organic phase are stripped in the order sodium, aluminiumand gallium. Hence, by stripping in two or more stages, a furtherseparation of gallium can be achieved and an aqueous solution having animproved purity of gallium can be achieved. This effect is illustratedin Example 10.

We have found that the ratio of extraction of gallium is dependent on anumber of factors. Thus, further substituents in the aromatic rings ofcompounds of the general formula A have been found to result in adecrease in the rate of extraction of gallium. Hence, the use of highlysubstituted compounds of the general formula A is not preferred sincesuch compounds generally result in a decrease in the rate of galliumextraction. The presence of a catalyst such as a tertiary carboxylicacid is also effective to give an increase in the rate of galliumextraction.

We have found that with some compounds of the general formula A, such asthe products of Examples 1 and 4, a maximum uptake of gallium into theorganic phase occurs after a relatively short contacting time, typicallyfrom 5 minutes to two hours, and thereafter the amount of galliumpresent in the organic phase decreases, typically to about half or lessof the maximum value. Accordingly it is desirable when using extractantsshowing this behaviour to use a contacting time which is substantiallythe same as the time which gives the maximum level of extracted gallium,preferably from 75% to 125% of the time which gives the maximum level ofextracted gallium.

We have found that the maximum level of gallium which can be extractedis dependent on a number of factors, in addition to the nature of thecompound of general formula A which is used. Thus, the use of a tertiarycarboxylic acid not only increases the rate of gallium extraction butmay also increase the maximum level of extracted gallium which can beattained. Furthermore, improving the efficiency of agitation, forexample by increasing the rate of stirring of the aqueous and organicphases, also results in an increase in the maximum level of extractedgallium which can be attained. The proportion of gallium extracted,expressed as the ratio of gallium concentration in the organic phase toaluminium concentration in the organic phase, has been found to increaseas the concentration, in the organic phase, of the compound of generalformula A decreases. However, it will be appreciated that although thiseffect results in gallium of higher purity in the organic phase, theconcentration of gallium extracted into the organic phase is reduced. Toachieve gallium of satisfactory purity at an acceptable concentration itis especially preferred that the concentration of the compound ofgeneral formula A in the extraction solution is in the range 20-200grams per liter.

The extractants of the present invention may be incorporated or absorbedon solid insoluble material, for example water insoluble polymers. Thisoffers the possibility of simplifying the extraction process as is wellknown in the art.

The invention is illustrated by the following non-limitative examples.

EXAMPLE I

A solution of 1,2-diaminoethane (30 g) in isopropanol (100 cm³) wasadded dropwise to a solution of 2-hydroxy-5-tertiarynonylbenzaldehyde(248 g) in isopropanol (300 cm³) so that the reaction temperature didnot rise above 35° C. Immediate production of a colour indicatedformation of the double Schiffs' base. After stirring for 18 hours atroom temperature the solution was treated with sodium borohydride (21.7g) which was added in portions over about 3 hours so that thetemperature did not rise above 30° C. The mixture was then stirred for18 hours at ambient temperature when almost complete discharge of theyellow colour indicated that reduction had taken place. Excessborohydride was decomposed by cautious dropwise addition of 120 cm³ ofwater, and the pH of the mixture was adjusted to 7 by addition ofglacial acetic acid. The mixture was then shaken with 800 cm³ ofchloroform and 400 cm³ of water, and the aqueous layer was separated anddiscarded. The chloroform solution was extracted with two 300 cm³portions of a 10% w/v aqueous solution of sodium carbonate and then withwater, separated and the chloroform was distilled under reducedpressure. Volatile impurities were finally removed by heating theconcentrate at 90° C. under a pressure of 0.3 mm of mercury, yielding280 g of N,N'-bis(2-hydroxy-5-tertiary-nonylbenzyl)-1,2-diaminoethane asa viscous oil. 31.4 g of this oil and 28.8 g of 2-acetoxybenzyl bromidewere dissolved in 90 cm³ of acetone and the solution was stirred andboiled under reflux. After 1.5 hours, 13.2 g of anhydrous sodiumcarbonate and 0.5 g of potassium iodide were added, and boiling underreflux was continued for a total of 36 hours from the start ofrefluxing. Towards the end of the reaction period, an addition of finelypowdered potassium carbonate (4.0 g) was made in order to complete thereaction. The mixture was then cooled and filtered, and the acetone wasdistilled under a reduced pressure of 20 mm of mercury. The product(53.7 g) was dissolved in ethanol (100 cm³) and a solution of sodiumhydroxide (11 g) in 20 cm³ water was added at such a rate that thetemperature did not rise above 65° C. The solution was allowed to cooland treated with acetic acid to reduce the pH to 7-8. Hexane (170 cm³),toluene (110 cm³) and ethyl acetate (20 cm³) were added and the mixturewas extracted firstly with 200 cm³ of water and then twice with 150 cm³portions of water. The organic layer was concentrated by distillation ofthe solvents and finally heated at 90°-100° C at 0.3 mm pressure. Oncooling, the product set to a brittle glass-like solid, which was shownby its nuclear magnetic spectrum in deuterochloroform to consistessentially of N,N'-bis-(2-hydroxy-benzyl)-N,N'-bis(2-hydroxy-5-tertiary nonylbenzyl)-1,2-diamino- ethane.

EXAMPLE 2

The ability of the product of Example I to extract gallium from aqueousalkaline solution was demonstrated as follows. A solution (A) simulatinga spent Bayer liquor was prepared by dissolving aluminium wire andgallium nitrate in aqueous sodium hydroxide so as to give a solutionwhich analysed as follows: (ppm refers to parts of metal weight ingrams, per million cubic centimeter of solution):

    ______________________________________                                        Alkali (as NaOH)   195 grams per liter;                                       Al.sub.2 O.sub.3   54 grams per liter;                                        Gallium            144 ppm.                                                   ______________________________________                                    

A solution of tetraphenol extractant, as obtained in Example 1, wasprepared by dissolving the extractant in a mixture of 9 parts by volumeof SOLVESSO 150 and 1 part by volume of n-decanol so as to give asolution (B) containing 73.7 grams of the extractant per liter ofsolution. Equal volumes of the solutions (A) and (B) were separatelyheated to 50° C. and then stirred together at this temperature. After 15minutes contact, the stirring was stopped and the organic and aqueouslayers were allowed to separate. It was found that the organic solutioncontained 80 ppm of gallium and 1325 ppm of aluminium, that is that morethan half of the available gallium but less than 5% of the availablealuminium was extracted. The rate of extraction of gallium at ambienttemperature was also investigated using an aliquot of solution (B) asbefore and an aqueous solution similar to (A) but containing 126.5 ppmof gallium. After stirring equal volumes of the solutions together for 1hour at 20 ° C. it was found that the organic solution contained 74 ppmof gallium and 900 ppm of aluminium, and after 4 hours that the organicsolution contained 93.5 ppm of gallium and 1025 ppm of aluminium.Recovery of extracted metals from the loaded organic solution bystripping with a second aqueous solution was investigated using anorganic solution B which had been loaded as described above and wasfound to contain 71 ppm of gallium and 1300 ppm of aluminium. Thissolution was agitated at 20° C. with an equal volume of 1.0M aqueoushydrochloric acid. The solutions were separated and analysed after acontact time of 30 minutes, when it was found that, within experimentalerror all the metals initially present in the organic solution hadpassed into the aqueous solution.

EXAMPLE 3

An aqueous liquor similar to that described in Example 2, but containing207 g per liter of NAOH, 51 g per liter of Al₂ O₃ and 130 ppm of galliumwas stirred at 50° C. in a nitrogen atmosphere with an equal volume ofan extractant solution prepared by diluting 8.3 g of Kelex 100(predominantly 7-undecyl-8-hydroxyquinoline) to 100 cm³ with a solventcomprising 9 parts by volume of Escaid 100 and 1 part by volume ofn-decanol. The times required to extract different percentages of thetotal gallium present into the organic solvent are listed in row Abelow.

A further series of experiments was carried out which differed only inthat the extractant solution also contained 0.74 g per 100 cm³ ofsolvent of the product of Example 1. The results of this series ofexperiments are given in row B below.

    ______________________________________                                        percentage gallium extracted                                                                   20%    40%      60%   80%                                    A, time in minutes required                                                                    12.5   54      110   202                                     B, time in minutes required                                                                   <1       2.5     4     12                                     ______________________________________                                    

The results show that addition of a catalytic quantity of the product ofExample I produces an increase in the rate of extraction by Kelex 100under these conditions, the average increase being about twentyfold.

EXAMPLE 4

A solution of 1,2-diaminopropane (37 g) in methanol (500 cm³) was addeddropwise to a solution of 2-hydroxy-5-tert.nonylbenzaldehyde (248 g) inmethanol (500 cm³) at a rate such that the reaction temperature did notrise above 50° C. Immediate production of a yellow colour indicatedformation of the double Schiff's base. The mixture was then boiled underreflux for 2 hours to ensure completion of the reaction. The methanolwas distilled under reduced pressure (20 mm) yielding 271 g ofN,N'-bis-(2-hydroxy-5-tert.nonyl-benzylidene)-1,2-propylenediamine as anoil. All of the oil was dissolved in isopropanol (1500 cm³) and thensodium borohydride (42 g) was added in portions over about 3 hours sothat the temperature did not rise above 55° C. The mixture was thenstirred for 18 hours at ambient temperature when almost completedischarge of the yellow colour indicated that reduction had taken place.Excess sodium borohydride was decomposed by cautious, dropwise additionof water (250 cm³) and the pH of the mixture was adjusted to 7 byaddition of glacial acetic acid. The mixture was then shaken with amixture of ethyl acetate (800 cm³) and water (500 cm³). The aqueouslayer was separated and discarded. The ethyl acetate solution wasextracted with two 300 cm³ portions of 10% w/v aqueous sodium carbonatesolution and then with water (300 cm³). The ethyl acetate was distilledunder reduced pressure (20 mm). Volatile impurities were finally removedby heating the concentrate at 90° C. under a pressure of 0.3 mm.Hg forone hour, yielding 215 g of N,N'-bis-(2-hydroxy-5-tert.nonylbenzyl)-1,2-diaminopropane as a viscous oil.

61 g of this viscous oil was dissolved in acetone (500 cm³) and asolution of 2-acetoxybenzyl bromide (57 g) dissolved in acetone (100cm³) was added dropwise at ambient temperature. The mixture was thenboiled under reflux. After 1 hour anhydrous sodium carbonate (26.4 g)and potassium iodide (5.0 g) were added, and boiling under reflux wascontinued for a total time of 32 hours. Towards the end of the reactionperiod an addition of finely powdered anhydrous potassium carbonate (8.0g) was made in order to complete the reaction. The mixture was thencooled and filtered, and the acetone was distilled from the filtrateunder reduced pressure (20 mm and 60° C). The concentrate (111 g) wasdissolved in ethanol (500 cm³) and a solution of potassium hydroxide(13.8 g) in water (45 cm³) was added at such a rate that the temperaturedid not rise above 65° C. The solution was allowed to cool and treatedwith acetic acid to reduce the pH to 7-8. Ethyl acetate (1500 cm³) wasadded and the mixture was extracted with water (500 cm³), then with a10% w/v aqueous sodium carbonate solution (300 cm³) and finally againwith water (500 cm³). The ethyl acetate was distilled under reducedpressure (20 mm at 60° C.). The concentrate was heated at 90° C. under apressure of 0.3 mm.Hg for one hour to remove any volatile impurities. Oncooling, the product set to 81.2 g of a brittle glass-like solid, shownby its nuclear magnetic resonance spectrum in deuterochloroform toconsist essentially ofN,N'-bis-(2-hydroxybenzyl)-N,N'-bis(2-hydroxy-5-tert.nonylbenzyl)-1,2-diaminopropane.

EXAMPLE 5

The ability of the product of Example 4 to extract gallium from aqueousalkaline solution was demonstrated as follows.

A solution (A) simulating spent Bayer liquor was used, this solutionbeing as described in Example 2. A solution of the tetraphenolextractant obtained in Example 4 was prepared by dissolving a sample ofthe extractant in a mixture of 9 parts by volume of SOLVESSO 150 (asdefined) and I part by volume of n-decanol so as to give a solution (B)containing 76.8 g of the extractant per liter of solution. Equal volumesof the solutions (A) and (B) were separately heated to 50° C. and thenstirred together at this temperature. After 3 hours contact, thestirring was stopped and the organic and aqueous layers were allowed toseparate. It was found that the organic solution contained 106 ppm ofgallium and 1675 ppm of aluminium, that is more than two-thirds of theavailable gallium but less than 6% of the available aluminium had beenextracted.

EXAMPLE 6

N,N'-bis(2-hydroxy-5-tert.nonylbenzyl)-1,2-diaminoethane (10.4 g)prepared as described in the first part of Example 1, and p-chlorophenol(15.4 g) were dissolved in ethanol (30 cm³). The solution was cooled to0° C. and aqueous formaldehyde (3.8 g of 32% w/w solution) was addeddropwise during 10 minutes. The solution was stirred at ambienttemperature for 20 hours, then boiled under reflux for one hour, cooledand extracted with a mixture of hexane (120 cm³) and ethyl acetate (30cm³). The organic solution was then extracted with four 60 cm³ portionsof 1M aqueous sodium hydroxide solution (to remove excessp-chlorophenol) and then shaken with water (50 cm³). Sufficient 1Maqueous hydrochloric acid was added to reduce the pH of the aqueouslayer, after shaking the mixture to between 7 and 8. The organic layerwas separated and concentrated by distillation of the solvent, finallyby heating at 95 ° under a pressure of 0.05 mm of mercury. The product(12.2 g) set on cooling to a glass-like amber resin. Nmr spectroscopyshowed that the resin contained the tetraphenolN,N'-bis(2-hydroxy-5-chlorobenzyl)-N,N'-bis(2-hydroxy-5-tertiarynonylbenzyl)-1,2-diaminoethane together with impurities.

A solution of the resin in a 9:1 by volume mixture of SOLVESSO 150 (asdefined) and n-decanol containing 8.06 g of the resin for each 100 cm³of the solution was gently shaken for 100 hours at 50° C. with an equalvolume of an aqueous solution which was 0.2 Molar in gallium (as galliumnitrate) and 2.5M in sodium hydroxide.

Analysis of the organic solution after this time by mass spectroscopyshowed that it contained 4150 ppm of gallium. From this, on the basisthat the extractant is the specified tetraphenol (M.Wt. 806) and forms a1:1 complex with gallium, it was calculated that the purity of the resinis 59.5% of the theoretical value.

EXAMPLE 7

This example shows that the rate of extraction of gallium by the resinof Example 6 can be increased by the addition of an organic acid.

An aqueous liquor similar to that described in Example 2, but containing153 g per liter of sodium hydroxide, 66 g per liter of Al₂ O₃ and 140ppm of gallium, was stirred at 50° C. in a nitrogen atmosphere with anequal volume aliquot of an extractant solution prepared as described inExample 6. The times required to extract different percentages of thetotal gallium present into the organic solution are listed in row Abelow.

A further series of experiments was carried out which differed only inthat 4.01 g per 100 cm³ of solution of a tertiary decanoic acid mixture(Versatic Acid 10 manufactured by Shell Chemicals) were added. Theresults obtained using this mixture are given in row B below.

    ______________________________________                                        Time         2 minutes 10 minutes                                                                              30 minutes                                   ______________________________________                                        % Total gallium                                                                             1.4       2.1       4.3                                         extracted, A                                                                  % Total gallium                                                                            18.2      29.6      29.3                                         extracted, B                                                                  ______________________________________                                    

EXAMPLE 8

This example demonstrates an alternative synthesis of the product ofExample 1.

N,N'-bis(2-hydroxy-5-tert.nonylbenzyl)-1,2-diaminoethane (333.07 g),prepared as described in the first part of Example 1, was heated withstirring at 110° C. to 120° C. 2-Hydroxybenzylalcohol (88.43 g) wasadded to this liquor, portionwise, over 5 minutes. After 6 hours at 110°C. to 120° C., a further addition of 2-hydroxybenzylalcohol (88.43 g)was carried out over 5 minutes. Stirring and heating were continued fora total of 23 hours. The mixture was then allowed to cool and ethylacetate (750 cm³) was added followed by hexane (400 cm³). An orangesolution was formed which was washed separately with 1M aqueous sodiumhydroxide solution (5×500 cm³) followed by saturated aqueous sodiumhydrogen carbonate solution (2×500 cm³). The organic solution was thenconcentrated under reduced pressure, finally at 0.5 mm at 95° C. for twohours, to yield 412.22 g of a viscous oil which set to a glass-likesolid condensate.

This condensate was found by liquid chromatographic analysis to containN,N'-bis(2-hydroxybenzyl)-N,N'-bis(2-hydroxy-5-tert.nonylbenzyl)-1,2-diaminoethane,although in a lesser proportion than the product of Example 1.

EXAMPLE 9

This Example shows the additional advantage gained by using a mixture ofan organic acid and a product of the present invention as a combinedcatalyst for the extraction of gallium using a7-alkyl-8-hydroxyquinoline as the primary extractant.

The aqueous liquor described in Example 7 was stirred at 20° C. in anitrogen atmosphere with an equal volume aliquot of an extractantsolution prepared by diluting KELEX 100 (as defined in Example 3) (4.17g) and a tertiary decanoic acid mixture (2.08 g) (Versatic acid 10) to50 cm³ with a solvent comprising 9 parts by volume of ESCAID 100 (asdefined) and 1 part by volume of n-decanol. The amounts of gallium foundin the organic solution (in ppm) after different contact times arelisted in row A below.

A further series of experiments was carried out which differed only inthat 0.42 grammes of the product of Example 8 were included in theorganic solution. The results obtained using this mixture are given inrow B below.

    ______________________________________                                        Time         1 min.  2 min.  5 min.                                                                              10 min.                                                                             30 min.                              ______________________________________                                        A, ppm Gallium                                                                             64      86      112   119   118                                  in organic solution                                                           B, ppm Gallium                                                                             84      97      121   118   120                                  in organic solution                                                           ______________________________________                                    

It will be observed that the addition of a small proportion of theproduct of the present invention has produced an increase in the initialrate of extraction of the gallium.

EXAMPLE 10

This demonstrates that a loaded organic solution of an extractant inaccordance with the present invention can be completely stripped by aslight excess of an aqueous acid solution and that by the carefuladdition of the aqueous acid solution the metals sodium, aluminium andgallium can be removed in turn.

22.5 g of the product of Example 4 was made up to a volume of 300 cm³with a 9:1 v/v mixture of SOLVESSO 150 and n-decanol. This solution wasloaded by stirring at 50° C. for two hours with 1500 cm³ of a solutionsimulating spent Bayer liquor, this solution being as described inExample 2.

The organic solution was separated and was found to contain 93.6 ppm ofgallium, 1348 ppm of aluminium and 2788 ppm of sodium. It was calculatedfrom this analysis that an aliquot of the organic solution would need tobe contacted with an equal volume aliquot of 0.275 molar aqueoushydrochloric acid in order to extract all of the metals according to thestoichiometric equations

    LMNA (organic)+HCl (aqueous)→LHM (organic)+NaCl (aqueous)

    and

    LHM (organic)+3HCl (aqueous)→LH.sub.4 (organic)+MCl.sub.3 (aqueous)

where

L is the product of Example 4 and

M is aluminium or gallium.

To 25 cm³ aliquots of the loaded organic solution obtained as described,were added 25 cm³ aliquots of aqueous hydrochloric acid of differingmolarity and stirring was effected for two hours at 25° C. The aqueousand organic phases were then analysed for metal content from which thepercentage of the total of each metal extracted into the aqueous phasecould be calculated. The results obtained are set out in tabular formbelow.

    ______________________________________                                        Molarity                                                                      of acid   % of each metal in aqueous phase                                    solution  Ga           Al       Na                                            ______________________________________                                        0.10      <1           <0.5     16                                            0.15      <1           18       >99.5                                         0.20      <1           49       >99.5                                         0.25      <1           74       >99.5                                         0.30      3            92       >99.5                                         0.35      82           >99.5    >99.5                                         0.40      98.4         >99.5    >99.5                                         0.45      >99.5        >99.5    >99.5                                         ______________________________________                                    

It will be observed that essentially all of the sodium is extractedbefore any appreciable amount of gallium is removed. It will also benoted that most of the aluminium has been extracted before a substantialproportion of the gallium is removed. Furthermore, in the presence of anexcess of acid of between 0.05 and 0.2 molar, increasing amounts ofgallium are extracted from the organic phase into the aqueous phase,essentially all of the gallium being extracted into the aqueous phaseusing an excess of acid of 0.2 molar.

EXAMPLE 11

The procedure of Example 6 was repeated using p-cresol (12.96 g) ratherthan p-chlorophenol to obtain a product containingN,N'-bis(2-hydroxy-5-methylbenzyl)-N,N'-bis(2-hydroxy-5-ter.-nonylbenzyl)-1,2-diaminoethane.The ability of this product to extract gallium from an aqueous alkalinesolution, and its active capacity for gallium, were measured by ageneral test based on the test procedure of Example 6. In the procedureof this general test, a solution of the diaminoethane derivative in amixture of SOLVESSO 150 and n-decanol (9:1 v/v) was made up so as to be0.1 molar based on the molecular weight of the pure diaminoethanederivative (in this case MW 765). This solution was gently agitated at50° with an equal volume of an aqueous solution which was 0.2 molar ingallium (as gallium nitrate) and 2.5 molar in sodium hydroxide. Tocompensate for differences in the rate of extraction of differentdiaminoethane derivatives, samples of the organic solution werewithdrawn and analysed after 3.5 hours, 20 hours, 85 hours and 100hours. The highest take up of gallium reached, and the correspondinguptake of sodium are recorded in Table 1, together with the percentagetheoretical maximum uptake of gallium calculated on the same assumptionsas in Example 6. The general test was also carried out with the productsof Examples 1 and 4. The results show that the product of the example israther slow to extract gallium, but the product has a good activecapacity for gallium, and a higher selectivity against sodium than theproducts of Examples I and 4.

EXAMPLE 12

A modified method, in which formaldehyde was reacted in two stages, wasused to prepare a product containingN,N'-bis(2-hydroxy-5-methylbenzyl)-N,N'-bis(2-hydroxy-5-ternonylbenzyl)-1,2-diaminoethane.NN'-bis(2-hydroxy-5-ternonylbenzyl)-1,2-diaminoethane (5.2 g) wasdissolved in ethanol (20cm³). Aqueous formaldehyde (0.77 g, strength39.4% w/w) was added and the mixture was boiled under reflux for 1.5hours. p-Cresol (10.8 g) was added followed by a further amount offormaldehyde solution (0.77 g) and boiling under reflux was continuedfor 20 hours. The product formed was concentrated to a glassy resin bydistillation of the solvent and excess p-cresol at 90° C. under apressume of 0.2 mm. The ability of the reaction product to extractgallium from aqueous alkaline solution was tested by the methoddescribed in Example 11 with the exception that the organic solution wasmade up to be 0.9 molar in the product of this example and 0.01 molar inthe product of Example 1, the latter being included as a rate catalyst.The results, listed in Table 1, show that a mixture of very high activecapacity for gallium had been obtained, and that the rate of extractionhad been increased compared to Example 11.

EXAMPLE 13

A product containingN,N'-bis(2-hydroxy-5-methoxybenzyl)-N,N'-bis(2-hydroxy-5-ternonylbenzyl)-1,2-diaminoethanewas prepared following the procedure of Example 12, but usingp-methoxyphenol (7.45 g) in place of the 10.8 g of p-cresol. The abilityof the product to extract gallium from aqueous alkaline solution wastested by the method of Example 11, and the results are listed inTable 1. A second test was carried out in which an organic solutionwhich was 0.1 molar in the product of this example, and 0.01 molar inthe product of Example I was used. Both tests gave the same value (56%theoretical) for gallium uptake after 20 hours. It was noted howeverthat after 3.5 hours the first test solution contained only 2.73 g/lgallium whereas the second test solution contained 4.05 g/l gallium.

EXAMPLE 14

A product containingN,N'-bis(2-hydroxy-3,5-dimethylbenzyl)-N,N'-bis(2-hydroxy-5-ternonylbenzyl)-1,2-diaminoethanewas prepared by the procedure of Example 12 but using 2,4-dimethylphenol(7.3 g) in place of the 10.8 g of P-cresol. The product obtained wastested by the procedure of Example 11 and results are listed in Table 1.

EXAMPLE 15

N,N'-bis(2-hydroxybenzyl)-1,2-diaminoethane, a white solid having m.p.120°-121°, was prepared by the procedure described in Example 1 of U.S.Pat. No. 4,338,460. A suspension of this compound (8.1 g) in methanol(20 cm³) was stirred at ambient temperature with saturated sodiumbicarbonate solution (10 cm³) and water (10 cm³). Aqueous formaldehydesolution (5.6 g of 32.2% w/w solution) was added dropwise forming agelatinous suspension which was stirred for 15 minutes and then addedduring 15 minutes to a solution of ter-dodecylphenol (15.7 g) inmethanol (120 cm³) heated to 60°-650°. The mixture was boiled underreflux for 20 hours and then cooled to ambient temperature. A viscousoil separated and the solvent was decanted from this viscous oil whichwas then extracted with acetone (100 cm³). The acetone extract wasfiltered and the acetone was distilled, leaving a white solid (9.53 g)containingN,N'-bis(2-hydroxybenzyl)-N,N'-bis(2-hydroxy-5-terdodecylbenzyl)1,2-diaminoethane.The capacity of this product to extract gallium from aqueous alkalinesolution was tested by the method of Example 11 and the results obtainedare recorded in Table 1. Although the highest take up of gallium wasobserved after 20 hours it was noted that almost as high a take up hadoccurred after 2.5 hours when the organic solution contained 2.66 g/lgallium.

EXAMPLE 16

2-Methyl-4-ternonylphenol was prepared by stirring a mixture of2-methylphenol (186 g), propylene trimer (263 g) and 2-toluenesulphonicacid (35.1 g) and heating at 95° C. for 24 hours. The y, mixture wasthen cooled and diluted with toluene (500 cm³), the toluene solution wasextracted three times with sodium hydroxide (500 cm³ portions of 10% w/vaqueous solution), then with hydrochloric acid (500 cm³ of 2N acid),dried with magnesium sulphate, filtered and distilled. The fractionhaving a boiling point of 132° C. at 0.2 mm pressure (251 g) wascollected.

2-Methyl-4-ternonylphenol (117 g obtained as described), methanol (900cm³) and freshly prepared 4-nitroso-N,N-dimethylaniline (150 g) whichhad not been dried after preparation but maintained as a paste inmethanol (30 g), and aqueous formaldehyde (150 cm³ of a 40% w/wsolution) were stirred together beneath a reflux condenser. Hydrogenchloride gas was passed through the suspension at such a rate as to boilthe solvent (62° C.). Reflux temperature and the passage of hydrogenchloride were maintained for 2 hours when all the solid had passed intosolution. The solution was cooled and diluted with water (400 cm³) andextracted with chloroform (500 cm³). The chloroform solution wasextracted with water until acid free, dried using anhydrous magnesiumsulphate and distilled. 2-Hydroxy-3-methyl-5-ternonylbenzaldehyde (112g) was collected as the fraction of boiling point 122° C. at 0.05 mmpressure.

2-Hydroxy-3-methyl-5-ternonylbenzaldehyde (20 g obtained as described)was reacted with 1,2-diaminoethane (2.29 g) in methanol (100 cm³), andthe double Schiffs base obtained (19 g) was reduced with sodiumborohydride (2.9 g) in isopropanol (130 g) using the procedure ofExample 4, to yieldN,N'-bis(2-hydroxy-3-methyl-5-ternonylbenzyl)-1,2-diaminoethane (16.3g). The procedures of Example 4 were also used to react this compound(6.84 g) with 2-acetoxybenzyl bromide (6.24 g) and to hydrolyse theproduct, yieldingN,N'-bis(2-hydroxybenzyl)-N,N'-bis(2-hydroxy-3-methyl-5-ternonylbenzyl)-1,2-diaminoethaneas a glassy solid (7.0 g). The product was shown to extract gallium fromalkaline solution by the procedure of Example 11. The results are givenin Table 1.

EXAMPLE 17

The procedures of Example 4 were used to react2-hydroxy5-ternonylbenzaldehyde (15.0 g) with 1-phenyl-1,2-diaminoethane(4.1 g) to give a double Schiffs base which was reduced with sodiumborohydride and then reacted with 2 equivalents of 2-acetoxybenzylbromide to yield a glassy material (19.3 g) containing N,N'-bis(2-hydroxybenzyl)-N,N'-bis(2-hydroxy-5-ternonylbenzyl)-1-phenyl1,2-diaminoethane.The product was shown to extract gallium from aqueous alkaline solutionby the procedure of Example 11. Results are given in Table 1.

EXAMPLE 18

This example demonstrates a further method of preparation of a materialcontaining the product of Example 1. N,N'-bis(2-hydroxy-5-ternonylbenzyl)-I,2-diaminoethane (10.5 g), prepared asdescribed in the first part of Example 1, and salicylaldehyde (5.4 g)were dissolved in ethanol (40 cm³) and the solution was agitated in aglass lined vessel in the presence of Raney nickel (3 g) under hydrogen(10 MNm⁻² pressure) at 120° for 5 hours. The product was digested withhydrochloric acid (100 cm³ of 7% w/w aqueous solution) and ethyl acetate(100 cm³). The mixture was filtered, the organic solution was separated,washed with aqueous sodium carbonate solution (2 molar, 50 cm³) andconcentrated under reduced pressure (90° C. at 0.5 mm) to a glassymaterial (12.0 g) containingN,N'-bis(2-hydroxybenzyl)-N,N'-bis(2-hydroxy-5-ternonylbenzyl)-1,2-diaminoethane.The product was tested by the method of Example 11. The results listedin Table I show that the product has a substantial capacity forextraction of gallium but is not as pure as the material prepared by themethod of Example 1.

EXAMPLE 19

A solution of N,N'-bis(2-hydroxy-5-ternonylbenzyl)-1,2-diaminoethane(10.5 g, 0.020 moles), prepared as described in the first part ofExample 1, was dissolved in ethanol (50 cm³) and aqueous formaldehydesolution (1.57 g of 40% w/w solution, 0.020 moles) was added withstirring. (In a comparative experiment which was terminated at thisstage, it was shown that N,N'-bis(2-hydroxy-5-ternonylbenzyl)imidazolidine had been formed). After 15minutes, p-cresol (10.6 g) was added and the solution was boiled underreflux for 91 hours. The solution was cooled, diluted with hexane (100cm³) and ethyl acetate (20 cm³) and extracted successively with 50portions of water, 1M sodium hydroxide solution, and saturated sodiumbicarbonate solution. The organic layer was then separated and thesolvents and excess p-cresol were distilled at 90° C. and 0.5 mmpressure leaving 10.2 g of a thick oil believed to consist essentiallyof N,N'-bis(2-hydroxy-5-ter-nonylbenzyl)-N-(2-hydroxy-5-methylbenzyl)-1,2-diaminoethane. Thismaterial was tested for its capacity to extract gallium from aqueousalkaline solution by the method of Example 11 and results are listed inTable 1. For comparative purposes, the starting materialN,N'-bis(2-hydroxy-5-ternonylbenzyl)-1,2-diaminoethane and theintermediate imidazolidine, isolated from the comparative experiment,were also submitted to the same test.

The results show that the diphenol and the imidazolidine extract onlyvery small amounts of gallium in contrast to the much greater proportionof gallium extracted by the products of the present invention, which aretri- and tetra-phenols.

EXAMPLE 20

The triphenolN-(2-hydroxybenzyl)-N,N'-bis(2-hydroxy-5-ternonylbenzyl)-1,2-diaminoethanewas prepared using a more specific synthesis than the route used inExample 18. The synthesis used is such as to exclude the possibilitythat the product contains other than in a very small amount, atetraphenolic compound as an impurity.

N-Propionyl-1,2-diaminoethane (58 g, 0.5 moles) was added, over a periodof 10 minutes to a stirred solution of 2-hydroxy-5-ternonylbenzaldehyde(130 g, estimated strength 96%, 0.5 moles) in methanol (100 cm³). Thetemperature rose spontaneously from 25° to 50° C. The solution wasallowed to cool, was stirred for 20 hours and then concentrated bydistillation of the methanol under reduced pressure (60° C., 0.5 mmpressure) to give a thick oil (179 g). The bulk of this oil (173 g) wasdissolved in isopropanol (500 cm³), stirred and heated to 40°-50° C. ina nitrogen atmosphere. Sodium borohydride (5.0 g) was added portionwiseduring 2.5 hours with occasional cooling to maintain the temperaturebelow 50° C. The mixture was stirred for a further 2 hours at 50° C.,then cooled and any excess borohydride was destroyed by the cautiousaddition of water (100 cm³). Sodium carbonate solution (2 molar, 100cm³) was added, and the pH was then adjusted to 7 by addition of dilutehydrochloric acid. Most of the isopropanol was distilled under reducedpressure, the residue was extracted into ethyl acetate (500 cm³), theethyl acetate solution was washed twice with water (each time 300 cm³)and concentrated at 90° C. and 0.5 mm pressure to giveN-(2-hydroxy-5-ternonylbenzyl)-N'-propionyl-1,2-diaminoethane, an oilwhich set to a glass on cooling (169 g).

104 g of the product thus obtained was dissolved in acetone (950 cm³),boiled and stirred under reflux whilst 2-acetoxybenzyl bromide (68.7 g)was added during 10 minutes. Anhydrous potassium carbonate (37.1 g) andpotassium iodide (18.5 g) were added and the mixture was stirred andboiled under reflux for 20 hours. It was then cooled, filtered and theacetone removed under reduced pressure (20 mm pressure). The residue wasredissolved in ethanol (500 cm³), and the solution was stirred andheated to 40° C. To this solution was added dropwise a solution ofsodium hydroxide (17.5 g) in water (50 cm³) at such a rate as tomaintain the temperature at 40°-45° C. The solution was then stirred at45°-50° C. for 2 hours. Concentrated hydrochloric acid was then added toreduce the pH to 8-9 (22 cm³ required). The solution was filtered, thefiltrate was concentrated under reduced pressure (20 mm pressure) toremove most of the ethanol and extracted into chloroform (500 cm³). Thechloroform solution was extracted with water (3×400 cm³) and thenconcentrated at 90° C. and 0.5 mm pressure toN-(2-hydroxybenzyl)-N-(2-hydroxy-5-ternonyl-benzyl)-N'-propionyl-1,2-diaminoethane(116.5 g).

A solution of the amide (28.2 g) in methanol (200 cm³) was warmed to 40°C. and concentrated hydrochloric acid solution (36% strength, 40 cm³)was added. The temperature rose spontaneously to 52° C. Water (20 cm³)was added and the solution was boiled under reflux for 20 hours. Thesolution was then cooled, water (50 cm³) was added and the mixture wasadjusted to pH 8 with sodium hydroxide solution (32%). A heavy oil wasprecipitated. The mixture was stirred for 18 hours at ambienttemperature and the solvent layer was decanted. The residual oil wasextracted with ethyl acetate (100 cm³), the solution was filtered andconcentrated under reduced pressure (20 mm pressure) to a reddish solid(23.7 g). The solid was dissolved in a mixture of hexane (50 cm³) andethyl acetate (50 cm³), stirred at ambient temperature for 18 hours withsaturated sodium carbonate solution (50 cm³), then with water (100 cm³)and again concentrated (90° C., 1.0 mm pressure) to yield crudeN-(2-hydroxy-benzyl)-N-(2-hydroxy-5-ternonylbenzyl)-1,2-diaminoethane(20.3 g).

All of the diphenol-diaminoethane derivative (nominally 0.051 moles) wasdissolved in ethanol (300 cm³) and boiled under reflux for 3 hours with2-hydroxy-5-ternonylbenzaldehyde (12.64 g, 0.051 mol). The solvent wasthen distilled (90° C., 1.0 mm pressure) yielding the crude Schiffs base(32.5 g). The proton nmr spectrum of this material measured indeuterochloroform with tetramethylsilane as internal standard, showedabsorptions due to the group --N═CH-- of the Schiffs base (δ=8.2) andexcess of the aldehyde (--CHO, δ=9.8) in approximate integral ratio of4:1, indicating that the purity of the crude primary amine had beenabout 80% of theoretical as measured by the amount of primary aminegroups present. The product was dissolved in isopropanol (300 cm³) andreduced with sodium borohydride (2.2 g) as previously described. Thecrude product after distillation of solvent was purified by dissolutionin hexane (200 cm³) and passage of hydrogen chloride gas through thesolution when amine hydrochlorides were precipitated, collected byfiltration, reslurried with hexane (200 cm³) and again collected. Thesolid was stirred with saturated sodium carbonate solution (100 cm³) andthe mixture was extracted firstly with hexane (100 cm³) at ambienttemperature and then with ethyl acetate (100 cm³) at 60° C., when allpassed into solution. The organic extracts were combined, dried (usinganhydrous MGSO₄) and concentrated by distillation of solvent at 90° C.and 1.0 mm pressure to a reddish glassy solid (22.3 g) consistingessentially ofN-(2-hydroxybenzyl)-N,N'-bis(2-hydroxy-5-ternonylbenzyl)-1,2-diaminoethane

The capacity of this material to extract gallium from aqueous solutionwas tested by the procedure of Example 11, with the exception that thesolutions were analysed after contact times of 1.5, 2,5 and 18.5 hours.The results are listed in Table 1.

                  TABLE 1                                                         ______________________________________                                                Highest                                                                       take-up    Corresponding                                                                             Time                                           Example of gallium take-up of  to    %                                        or      observed (g/l                                                                            sodium (g/l highest                                                                             theoretical                              Comp. Ex.                                                                             in organic in organic  take-up                                                                             gallium                                  (a)     solution)  solution)   (hours)                                                                             extracted                                (a)     (b)        (b)         (b)   (c)                                      ______________________________________                                         1      4.35       2.60        3.5   62                                        4      4.60       1.75        3.5   66                                        6      4.15       2.12        100   59.5                                     11      4.45       1.32        85    64                                       12 + 1  5.85       2.23        20    84                                       13      3.90       1.60        20    56                                       13 + 1  4.33       1.90        20    56                                       14      4.33       1.48        20    62                                       15      2.97       1.67        20    43                                       16      4.00       1.53        20    57                                       17      2.68       3.93        3.5   38                                       18      3.30       1.30        3.5   47                                       19      3.13       1.50        3.5   45                                       A       0.33       1.80        20    4.7                                      B       0.19       0.53        20    2.7                                      20      4.13       1.43        1.5*  59                                       ______________________________________                                         Notes to Table 1                                                              (a) The number is the example in which the preparation of the extractant      is described. In all cases the extractant was used as a 0.1 Molar solutio     with the exception of (13 + 1) which was 0.1 Molar in the Example 13          product and 0.01 Molar in the Example 1 product. (12 + 1) is a mixture of     0.09 Molar of the Example 12 product and 0.01 Molar of the Example 1          product. A is N,Nbis(2-hydroxy-5-ternonylbenzyl)-1,2-diaminoethane. B is      N,Nbis(2-hydroxy-5-ternonylbenzyl)-imidazolidine.                             (b) Samples were taken at various times and analysed to determine the         amount of gallium extracted. The quantities recorded are the maximum          amount of gallium extracted, the amount of sodium extracted at the maximu     of gallium and the time (in hours) at which the maximum of gallium was        attained. *Samples were taken after 1.5, 2.5 and 18.5 hours.                  (c) This is based on the assumptions set out in Example 6, namely the         compound, or mixture of compounds, forms a 1:1 complex with gallium. Sinc     a 0.1 Molar solution of compound (0.11 Molar solution of total compounds      when using the mixture of 13 + 1) is used, the theoretical concentration      which the gallium could attain in the organic solution is 0.1 Molar (or       0.11 Molar).                                                             

EXAMPLE 21

The procedure of Example 4 was repeated. The product obtained wassubjected to the test described in Example 5 with the modification thatthe organic solution was adjusted periodically for gallium andaluminium, giving the results listed in columns A below. A second testwas carried out at the same time, which differed only in that theorganic solution contained 38.4 g/l of bis(2-ethylhexyl)phosphoric acidin addition to the 76.8 g/l of extractant. The results are listed incolumns B below.

    ______________________________________                                        Time   Metal concentration in organic solution (ppm)                          (minutes)                                                                            A gallium A aluminium                                                                              B gallium                                                                             B aluminium                               ______________________________________                                         15      50.5     975       54       800                                       30    67        1100       71.5     925                                       60    82        1200       85.5    1050                                      120    85        1275       92      1175                                      300      79.5    1200       83.5    1225                                      ______________________________________                                    

The results show that inclusion of the bis(2-ethylhexyl) phosphoric acidproduced an increase in the rate of extraction of gallium, and in themaximum uptake of gallium obtained.

EXAMPLE 22

The test procedure of Example 5 was repeated using a single I organicsolution containing 76.8 g/l of the product of Example 20, together with38.4 g/l of VERSATIC ACID 10, with the further difference that thetemperature at which the organic solution and the simulated Bayer liquorwere stirred together was 65° C. The metal concentrations obtained afterincreasing contact times are listed below.

    ______________________________________                                        Time    Metal concentration in organic solution                               (minutes)                                                                             Gallium (ppm)                                                                              Aluminium (g/l)                                                                            Sodium (g/l)                                ______________________________________                                         2      54.5         1.05         7.1                                          5      74.5         1.10         6.7                                         10      103.5        1.20         6.8                                         30      104.5        1.28         6.7                                         60      97           1.30         6.8                                         120     80.5         1.35         6.9                                         240     56.5         1.30         6.8                                         1200    34.5         1.45         6.1                                         ______________________________________                                    

The results show a maximum in the amount of gallium extracted and in theratio of gallium to aluminium extracted, such that under theseconditions the aqueous and organic phases are most efficiently contactedfor a time between about 10 and about 30 minutes.

COMPARATIVE EXAMPLE C

The procedure of Example 4 was repeated with the exception that1,3-diaminopropane was used as a starting material rather than1,2-diaminopropane. The reactions were effected in the manner describedin Example 4 and a product containing essentiallyN,N'-bis(2-hydroxybenzyl)-N,N'-bis(2-hydroxy-5-ternonylbenzyl)-1,3-diaminopropanewas obtained.

The ability of this material to extract gallium from aqueous alkalinesolution was tested by the procedure of Example 5, using an organicsolution containing 76 g/l of the product per liter of solution. Theamounts of gallium and aluminium extracted into the organic solutionwere analysed after a series of increasing contact times with theresults listed below.

    ______________________________________                                        Time    Metal concentration in organic solution                               (minutes)                                                                             Gallium (ppm)                                                                              Aluminium (g/l)                                                                            Sodium (g/l)                                ______________________________________                                         5      <2.5         150          4.5                                         30      <2.5         150          4.5                                         60      <2.5         150          4.7                                         360     <2.5         150          5.3                                         ______________________________________                                    

The results show that the 1,3-diaminopropane derivative is ineffectiveas an extractant for gallium from strongly alkaline solution, incontrast to the 1,2-diaminoethane derivatives of the present invention.

What is claimed is:
 1. A process for the extraction of gallium from abasic aqueous solution containing gallium comprising the steps of:(a)contacting an aqueous solution containing gallium with a solution in awater immiscible solvent of at least one compound of the formula (A),##STR8## wherein: Q is a hydrogen atom, a hydrocarbyl group or a group--CH₂ Z;Z is a --COOH group or a 2-hydroxyphenyl group which mayoptionally be substituted by the groups R₁₂, R₁₃ and R₁₄ ; R₁ to R₉, andR₁₂ and R₁₄, which may be the same or different, are substituent groupsselected from hydrogen, hydrocarbyl, alkoxy, halogen, hydrocarbyl,sulphonyl, acyl, amino, nitro and cyano or, when R₁ and R₂ and/or R₄ andR₅ are adjacent substituents they may complete a benzo ring and R₁ to R₉and R₁₂ to R₁₄ are such that the substituents on at least one of therings are different from the substituents on at least one other of therings; R₁₀ And R₁₁ are each, independently, a hydrogen atom or an alkylgroup containing up to 20 carbon atoms; Y₁ is a hydrogen atom, or analkyl group containing up to 20 carbon atoms, or a phenyl group; Y₂ is ahydrogen atom or an alkyl group containing up to 20 carbon atoms, or Y₁and Y₂, together with the group ##STR9## to form saturated orunsaturated ring system; and R₁ to R₁₄, Y₁ and Y₂ are the same ordifferent and together contain in total from 10 to 60 saturated carbonatoms, (b) separating the aqueous phase from the solvent phase whichcontains a gallium complex compound; (c) contacting the solvent phasewith an aqueous mineral acid or with an aqueous solution which is morestrongly alkaline than the aqueous solution of steps (a) and (b); and(d) separating the solvent phase from the aqueous phase containing metalin the form of a salt of the mineral acid or of an oxyanion.
 2. Theprocess according to claim 1 wherein in the compound of Formula A,Q is Hor --CH₂ Z; Z is 2-hydroxyphenyl R₁ and R₄ are hydrocarbyl; R₂ and R₃are H; R₅ to R₁₁ are H; Y₁ is H or methyl; and Y₂ is H.
 3. The processaccording to claim 2 wherein R₁ and R₄ are the same and are selectedfrom the mixed and higher tertiary alkyl groups which are obtainablefrom propylene trimer, propylene tetramer and mixtures thereof.
 4. Theprocess of claim 3 wherein R₁ and R₄ are selected from tertiary octyl,tertiary nonyl and tertiary dodecyl.
 5. The process of claim 1 whereinthe compound of Formula A isN,N'-bis(2-hydroxybenzyl)-N,N'bis(2-hydroxy-5-tertiarynonylbenzyl)-1,2-diaminoethaneorN,N'-bis(2-hydroxybenzyl)-N,N'-bis(2-hydroxy-5-tertiarynonylbenzyl)-1,2-diaminopropane.6. The process of claim 1 wherein the solution of the compound ofFormula A in a water immiscible solvent further includes (a) a8-hydroxy-quinoline carrying a 7-(C₆₋₃₆ -alkyl)- or 7-(C₆₋₃₆ -alkenyl)-group or (b) a tertiary carboxylic acid.
 7. The process of claim 1wherein the solution of the compound of Formula A in a water immisciblesolvent further includes (a) a 8-hydroxy-quinoline carrying a 7-(C₆₋₃₆-alkyl)- or 7-(C₆₋₃₆ -alkenyl)- group and (b) a tertiary carboxylicacid.
 8. The process of claim 6 wherein the 7-(C₆₋₃₆ -alkyl)- or7-(C₆₋₃₆ -alkenyl)- group is selected from the group consisting ofnonyl, decyl, undecyl, dodecyl, dodecenyl, tridecyl, tetradecyl andoctadecyl.
 9. The process of claim 7 wherein the 7-(C₆₋₃₆ -alkyl)- or7-(C₆₋₃₆ -alkenyl)- group is selected from the group consisting ofnonyl, decyl, undecyl, dodecyl, dodecenyl, tridecyl, tetradecyl andoctadecyl.
 10. The process of claim 6 wherein the hydroxyquinoline is7-undecyl-8-hydroxyquinoline.
 11. The process of claim 6 wherein thehydroxyquinoline is 7-undecyl-8-hydroxyquinoline.
 12. The process ofclaim 6 wherein the tertiary carboxylic acid is of the formula:##STR10## wherein R₁₅, R₁₆ and R₁₇ are alkyl which together contain from6 to 45 carbon atoms.
 13. The process of claim 7 wherein the tertiarycarboxylic acid is of the formula: ##STR11## wherein R₁₅, R₁₆ and R₁₇are alkyl which together contain from 6 to 45 carbon atoms.